British anti-monarchists condemn the London police's oppressive treatment of the protesters, who had gathered in their thousands to denounce Charles III's coronation as the country's king.
The people against the antiquated monarchical system said on Sunday there is no longer a right to peaceful protest in Britain after dozens of protesters were arrested.
Overall, as many as 64 people were rounded up during the Saturday ceremony, which was held at Westminster Abbey before King Charles and Queen Camilla were driven back to Buckingham Palace, the police announced on Sunday.
The law enforcement described the alleged offenses that had led to the arrests as a breach of the peace and conspiracy to cause a public nuisance.
The arrestees included Graham Smith, leader of the Republic group, which campaigns for the abolition of the monarchical system in the United Kingdom.
"This was a heavy-handed action which had the appearance of a pre-determined arrest that would have occurred regardless of the evidence or our actions. The right to protest peacefully in the UK no longer exists," Smith said in a statement.
"These arrests were not about protecting people from harm, but about protecting the King from embarrassment."
Trying to explain the reason behind the arrests, the police, however, alleged that their so-called duty to prevent disruption outweighed the right to protest.
Republic said that its members began to be released late on Saturday evening after nearly 16 hours in custody.
The Metropolitan Police had deployed some 11,500 officers for one of its biggest-ever security operations for the day of the coronation.
The police had warned that it would have an "extremely low threshold" for protests, and controversially planned to use mass facial recognition technology to monitor the crowds.
"Our tolerance for any disruption, whether through protest or otherwise, will be low," the police force wrote on Twitter this week. "We will deal robustly with anyone intent on undermining this celebration."